Hajduk finished the season fourth in HT First League and therefore they will start Europa League qualifiers from the first qualifying round. The draw will take place on June 19 and the first leg on July 11 either in Dugopolje or away. The second leg will also take place in Dugopolje or away as Hajduk can't host a match at Poljud in that period. The new HT First League season 2019/2020 starts right after UEL QR1 second leg match. 

This is the detailed list of matches and fixtures in June, July and August 2019, according to currently available information:

JUNE:
... Pre-season preparations (in Split)
June 19: UEL QR1 and QR2 draw, pre-season camp in Slovenia

JULY:
July 11: UEL QR1 (first leg)
July 18: UEL QR1 (second leg)
July 21: HT First League, round 1 *

July 22: UEL QR3 draw

July 25: UEL QR2 (first leg)

July 28: HT First League, round 2

AUGUST:
August 01, 2019: UEL QR2 (second leg)
August 04: HT First League, round 3*

August 05: UEL Playoff draw

August 08: UEL QR3 (first leg)
August 11: HT First League, round 4*

August 15: UEL QR3 (second leg)
August 18: HT First League, round 5*

August 22: UEL Playoff (first leg)
August 25: HT First League, round 6*

August 29: UEL Playoff (second leg)

*HNK Hajduk doesn't have influence of HT First League fixtures and changes are possible. In the previous seasons, the teams that played UEL qualifiers on Thursdays always played their championship fixtures on Sundays.